That's pretty generous.They are giving you a window of 6 days to come scarf up your free grub instead of just 1 day that Golden Corral does over here. That gives you a certain flexibility in case you have only one restaurant in the area and a bunch of chow-hounds and freeloaders in the area that you have to elbow out of the way.
Can't think why they would have used an unshaven G.I. re-enactor as a model for their ad though. Maybe all the Brits were otherwise engaged.